The invention relates to a system and a process for the reduction of a rotational imbalance of a drive train of a hybrid vehicle. The drive train includes an internal-combustion engine, an electric machine, and a crankshaft.
A rotational imbalance is a summation of all periodical interfering torques as a result of mass moments of inertia, combustion peaks, and secondary effects that are created at the crankshaft by the operation of the internal-combustion engine. The rotational imbalances are superimposed on the output torque supplied by the internal-combustion engine with several periodical interferences. It is known to combat rotational imbalances by way of passive absorption elements, such as a dual mass flywheel (ZMS) or a rotational-speed-adaptive absorber (DAT).
Likewise, active compensation functions are known. Within the scope of an active process, automatically controlled actuators are used, as appropriate in connection with a passive member. Active compensation functions take into account the effect of the optionally installed passive members, such as the ZMS and the DAT, and carry out an active compensation of the interferences in symbiosis with the latter. In this case, signals of the drive train that are detected by sensors, such as rotational speeds, torques, or longitudinal accelerations are processed and compared with reference values, in order to trigger corresponding actuators as a function of a control fault. Controls of this type are generally limited in their useful bandwidth because of signal propagation times and actuator limitations. Depending on the drive topology (i.e. the construction of the engine, etc.) and the actuator quality, cut-off frequencies are typically between 10 Hz and 20 Hz, so that concepts of this type are suitable for the absorption of bucking frequencies and other low-frequency interferences, but cannot cover the entire frequency spectrum of the rotational imbalance.
It is therefore an object of the present invention to provide a system and a method which are structurally and/or functionally improved such that they can combat a wider frequency spectrum of rotational imbalances.
Embodiments of the invention provide a system for the reduction of a rotational imbalance of a drive train of a hybrid vehicle. The drive train includes an internal-combustion engine, an electric machine, and a crankshaft. A reduction or nullification of the rotational imbalance takes place by actuating the electric machine. The actuation is implemented as an adaptive feed forward control. The adaptive feed forward control provides an actuation signal for the electric machine. The actuation signal represents a desired torque to be generated by the electric machine, so that the electrical machine outputs a torque that is at least approximately inverse with respect to the rotational imbalance to the crankshaft for the superimposition of the torque generated by the internal-combustion engine.
Embodiments of the invention further provide a process for the reduction of a rotational imbalance of a drive train of a hybrid vehicle, the drive train including an internal-combustion engine, an electric machine, and a crankshaft. A reduction or nullification of the rotational imbalance takes place by an actuation of the electric machine. The actuation takes place by way of an adaptive feed forward control, which provides an actuation signal for the electric machine. The actuation signal represents a desired torque to be generated by the electric machine, so that the electric machine outputs a torque that is at least approximately inverse with respect to the rotational imbalance to the crankshaft for the superimposition of the torque generated by the internal-combustion engine.
Embodiments of the invention use the electric machine for the absorption of the rotational imbalance. In this case, the electric machine is not activated by way of a classic automatic control, which can typically absorb only low-frequency interferences of up to approximately 15 Hz, but by using an adaptive feed forward control by way of which oscillations in the audible range can also be reduced or absorbed. This approach is based on the recognition that the frequency components to be absorbed depend on the rotational engine speed, and the frequency to be absorbed is known ab initio. As a result, this knowledge can be used in the feed forward control in order to absorb or reduce the corresponding oscillations.
As a result, the quiet running of the internal-combustion engine can be increased. Likewise, unintended oscillations in the drive train can be damped. The system and the process can further be used for acoustically improving the noise of the internal-combustion engine. A further advantage is that passive absorption elements of the drive train, such as dual-mass flywheels or rotational-speed-adaptive absorbers, can be saved. This becomes possible because a high-quality function of the adaptive feed forward control can be used.
According to an advantageous further development, a rotational speed of the internal-combustion engine, which is detected by measuring, can be fed as an input variable to the feed forward control for processing. In particular, a frequency vector can be fed to the feed forward control, which can be generated from the rotational speed of the internal-combustion engine, with the frequencies that are contained in a signal representing the rotational imbalance. Correspondingly, in a further development of the process according to embodiments of the invention, a rotational speed of the internal-combustion engine, which is detected by measuring, is fed as an input variable to the feed forward control for processing. In particular, in the process according to embodiments of the invention, a frequency vector is fed to the feed forward control, which can be generated from the rotational speed of the internal-combustion engine, with frequencies that are contained in a signal representing the rotational imbalances. In this case, the frequency vector can be generated by way of a frequency generator.
In a further development of the system according to embodiments of the invention, for the adaptation of the feed forward control, a rotational speed of the electric machine detected by measuring can be fed to the feed forward control as a further input variable for the processing. The rotational speed contains a residual interference of the rotational imbalance. Analogously, in a further development of the process, for the adaptation of the feed forward control, a rotational speed of the electric machine detected by measuring is fed to the feed forward control as a further input variable for processing. The rotational speed contains a residual interference of the rotational imbalance.
In a further advantageous development, the adaptive feed forward control for the processing for predefined engine orders includes information concerning the frequencies contained in the interference signal representing the rotational imbalance. In the process, the adaptive feed forward control for predefined engine orders processes information concerning the frequencies contained in the interference signal representing the rotational imbalance.
In a further development, the adaptive feed forward control includes an interference variable monitor, which is designed for generating an A-matrix. In a manner known to the person skilled in the art, an A-matrix is used for the layout or definition of an automatic control. In this case, a damping is optionally taken into account in the A-matrix.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.